1. Field of the Invention
The present invention relates to a cooling system such as for air conditioning of a vehicle passenger room or refrigeration in a refrigerator car.
More specifically, the invention relates to an improvement in arrangement of a cooing system including an air compressor connected to a cooler, an air expander connected to the cooler and coupled with the compressor, and a speed change gear for driving the compressor.
2. Description of Relevant Art
It is difficult to find a prior-art technique of the present invention in the most concerned field. Therefore, relevant techniques in neighboring fields will be described below to help understand a background of the invention.
FIG. 1 illustrates a gas turbine apparatus 201 described in page 144, B7 of "Mechanical Engineering, Handbooks A (bases) and B (applications)" issued on Sep. 30, 1991, by the Japan Society of Mechanical Engineers, in Japan.
FIG. 2 illustrates a gas turbine apparatus 203 described in page 120 of a volume of "Rotary Engine/Gas Turbine" of six "Automobile Engineering Books" issued on Jan. 20, 1980, by Sankaido Co., Ltd, in Japan.
The gas turbine apparatus 201 of FIG. 1 includes a combustor 205, a turbine 207 to be driven with combustion gases from the combustor 205, a compressor 209 to be driven by the turbine 207, and a reduction gear 213 of a planetary gear type adapted to transmit drive torque from the turbine 207 in a speed reducing manner and provided with an output shaft 211 for outputting drive torque with a reduced revolution speed.
The compressor 209 is arranged between the turbine 207 and the reduction gear 213.
The compressor 209 has a housing 215 composed of separate members: a suction side member 217 and a discharge side member 219 fastened together with bolts 221. The reduction gear 213 includes a flange member 227 fixed by bolts 225 to the compressor housing 215, and pinion gears 223 supported by the flange member 227.
The turbine 207 and the compressor 209 generate thrust forces, which are born with thrust bearings arranged at the (left) side where the reduction gear 213 is installed.
The gas turbine apparatus 203 of FIG. 2 includes is a combustor 229, a turbine 231 to be driven by combustion gases from the combustor 229, a compressor 233 to be driven by the turbine 231, and a reduction gear set 237 adapted to transmit drive torque from the turbine 207 in a speed reducing manner and provided with an output shaft 235 for outputting drive torque with a reduced revolution speed.
The turbine 231 is arranged between the compressor 233 and the reduction gear set 237.
The turbine 231 is provided with a rotor 239, which has a separated shaft 241 on the (right) side to be connected to the reduction gear set 237. The separation of shaft 241 is effective to prevent unfavorable heat transmission from the turbine 231 end, where the rotor 239 is exposed to hot combustion gases, to the gear set 237 end, where associated bearings 243 as well as meshing gears should be kept free from adverse thermal influences.
The gas turbine apparatus 201 or 203 may be applied to an air conditioner or freezer using air as a coolant.
In the gas turbine apparatus 201 of FIG. 1, however, the compressor 209 which generates a negative pressure neighbors with the reduction gear 213 of which a casing 243 has therein an atmospheric pressure, and lubricant has a tendency to leak from within the casing 243 toward the compressor 209, due to the negative pressure.
In application of this apparatus 201 to an air conditioner or freezer, compressed air is expanded to be cooled by an expander, such as a turbine, and delivered therefrom to an air-conditioned room or freezing room. Therefore, the delivered cold air tends to have mixed oil.
For practical use of the cold air, the mixed oil should be removed by an oil separator or the cooling system in concern should have a closed cycle.
The oil separator is expensive. The closed cycle needs an evaporator for heat exchange, and tends to be complex and large-sized, resulting in a dear cost with a reduced efficiency (i.e. increase in COP: coefficient of power as a ratio of reduction to an input).
Moreover, in the application in concern, the reduction gear 213 has a shaft 245 thereof supported by a pair of left and right bearings 246, 247, whereby a sun gear 249 formed at a left end of the shaft 245 is supported in a cantilevered manner.
Therefore, the left bearing 246 bears an increased load in dependence on a shaft projection length therefrom to the sun gear 249, and the left and right bearings 246, 247 have different loads shared thereto, with increased losses of friction and drive torque, resulting in a reduced durability.
Further, the housing 215 of the compressor 209 is separated into the suction side and discharge side members 217, 219 and the pinion gears 223 of the reduction gear 213 are supported by the flange member 227 separated from the housing 215, needing a precise machining with high accuracy for a required centering of the respective separate members 217, 219, 227 as well as of respective gears in the reduction gear 213, resulting in an increased machining cost.
To this point, if the centering be incomplete, the gas turbine apparatus 201 would fail to perform a high-speed revolution, accompanying vibrations, causing a reduced durability.
Still more, the separate members 217, 219, 227 need the bolts 221, 225 for their fixing, resulting in the more increased number of component parts, with the more reduced adaptiveness for assemblage.
Yet more, the thrust bearings arranged at the reduction gear 213 side may constitute a difficulty, when assembling the gas turbine apparatus 201. Besides, possible errors in assemblage of the respective members may be accumulated on the side the compressor 209 and the turbine 207 are installed, with enlarged gaps between rotors and housings, having a reduced heat insulating efficiency.
On the other hand, in the gas turbine apparatus of FIG. 2, the rotor 239 of the turbine 231 is separated from the shaft 241 on the reduction gear set 237 side, thus needing a precise machining with high accuracy for a required centering of the rotor 239 and the shaft 241, while having an increased number of component parts, with a lowered accuracy in and reduced adaptiveness for their assemblage.